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MCAT TPR Biology > Eukaryotic Cells > Flashcards

Eukaryotic Cells Flashcards

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1
Q

Function of the nucleus?

A

contain and protect DNA, transcription, partial assembly of ribosomes

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2
Q

Function of mitochondria?

A

produce ATP via the Krebs cycle and oxidative phophorylation

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3
Q

Function of ribosomes?

A

synthesize proteins

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4
Q

Function of rough ER?

A

location of synthesis/modification of secretory, membrane bound, and organelle proteins

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5
Q

Function of smooth ER?

A

detoxification and glycogen breakdown in liver, steroid synthesis in gonads

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6
Q

Function of golgi apparatus?

A

modification and sorting of protein, some synthesis

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7
Q

Function of lysosomes?

A

contain acid hydrolases which digest various substances

responsible for degradation of biological macromolecules by hydrolysis

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8
Q

Function of peroxisomes?

A

metabolize lipids and toxins using H2O

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9
Q

The nucleus contains the genome surrounded by a ______ ______.

A

nuclear envelope (not accessible to the cytoplasm)

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10
Q

In Eukaryotes, replication, transcription, and splicing occur in the ______. Translation occurs in the _______.

A

Nucleus

Cytoplasm

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11
Q

Yeast have _____ chromosomes, humans have _____.

A

4

23

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12
Q

Centromeres?

A

structure near the middle of eukaryotic chromosomes to which the fibers of the mitotic spindle attach during cell division

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13
Q

Telomeres?

A

have large numbers of repeats of a specific DNA sequence that help maintain the ends of the linear chromosomes during replication (enzyme: telomerase)

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14
Q

Locus?

A

specific location on the chromosome that a gene is located

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15
Q

Heterochromatin?

A

regions of densely packed chromatin on a chromosome where genes are inaccessible and turned off

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16
Q

Euchromatin?

A

loosely packed chromatin on a chromosome that allow genes to be activated

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17
Q

If a retrovirus inserts is genome into regions of heterochromatin and nowhere else, how is this likely to affect the infection process?

A

the retroviral genes will not be expressed very frequently, the virus will remain as a provirus until a change happens

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18
Q

Role of the nuclear matrix?

A

support and provide overall structure

regulating gene expression

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19
Q

Nucleolus function?

A

functions as a ribosome factory, contains loops of DNA, RNA polymerases, rRNA, and protein components of the ribosome (no membrane separating it from the nucleus)

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20
Q

The nucleolus is larger in cells that do what?

A

producing large amounts of proteins due to the increased synthesis of ribosomes

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21
Q

What role do the loops of DNA in the nucleolus play?

A

the DNA serves as a template for rRNA production RNA pol

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22
Q

Where do the protein components of the ribosome come from during rRNA production?

A

they are transported into the nucleus from the cytoplasm because proteins are translated outside the nucleus

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23
Q

Does the ribosome finish assembly in the nucleus?

A

no it remains partially assembled and inactive until it gets to the cytoplasm, this is to prevent translation of hnRNA

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24
Q

What is the nuclear membrane?

A

membrane that separates the nucleus from the cytoplasm composed of two lipid bilayers

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25
Q

What is the space between the inner and outer nuclear membranes contiguous with?

A

ER lumen, isolated from the cytoplasm

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26
Q

What size of molecule can diffuse through nuclear pores?

A

molecules smaller than 60 kilodaltons, including small proteins

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27
Q

How can larger proteins get inside the nucleus?

A

they need to contain a sequence called the nuclear localization sequence which are translated on cytoplasmic ribosomes and then imported into the nucleus by a specific transport mechanism

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28
Q

Where is the site of oxidative phosphorylation?

A

mitochondria

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29
Q

What is the interior of the mitochondria called?

A

matrix

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30
Q

What does the matrix contain that is important to cell respiration?

A

pyruvate dehydrogenase and enzymes for the Krebs cycle

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31
Q

The inner membrane of the mitochondria is the location for what?

A

electron transport chain and ATP synthase

site for the proton gradient used to drive ATP synthesis

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32
Q

The inner membrane of the mitochondria is folded into what?

A

cristae

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33
Q

The inner of the mitochondria is impermeable to what?

A

free diffusion of polar substances like protons

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34
Q

The outer membrane of the mitochondria is smooth and allows diffusion of what?

A

has large pores that allow diffusion of small molecules

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35
Q

ATP produced in the mitochondria goes where?

A

transported into the cytoplasm to drive a great variety of cell processes

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36
Q

Why is the inner membrane folded into cristae?

A

to increase surface area of the inner membrane in order to increase electron transport and ATP synthesis

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37
Q

Are the enzymes of glycolysis found in the matrix?

A

no in the cytoplasm

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38
Q

How does pyruvate get into the matrix where pyruvate dehydrogenase is located?

A

transported through the membrane by a specific protein in the membrane

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39
Q

Mitochondria possesses their own _____.

A

genome

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40
Q

What is the mitochondria genome like?

A

smaller than the cell genome and consists of single circular DNA molecule

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41
Q

What does the mitochondria genome code for?

A

rRNA, tRNA, and several proteins including some components of the electron transport chain and parts of the ATP synthase complex (most are coded by nuclear genes)

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42
Q

T/F

Mitochondria use the same system of transcription and translation as the nucleus does.

A

False

they have their own

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43
Q

What is the mitochondria endosymbiotic theory?

A

originated as independent unicellular organisms living within larger cells

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44
Q

What bacteria do mitochondria resemble?

A

Gram negative bacteria

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45
Q

What difficulty may be encountered in translation of a mitochondrial gene moved to the nucleus?

A

coding system of cellular genome is different from that of the mitochondrial genome

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46
Q

Mitochondria are inherited _______.

A

maternally

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47
Q

Why is the mitochondria inherited maternally?

A

the cytoplasm of the egg becomes the cytoplasm of the zygote, sperm only contributes nuclear genes

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48
Q

If a woman has a disease caused by an abnormality in her mitochondrial genome, what are the chances her children will have the disease?

A

100%

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49
Q

Why is the rough ER called rough?

A

large number of ribosomes bound to its surface

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50
Q

The rough ER is the site for what?

A

protein synthesis for proteins targeted to enter the secretory pathway, directs protein traffic to different parts of the cell

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51
Q

The smooth ER can contain enzymes for what?

A

involved in steroid hormone biosynthesis (gonads) or in the degradation of environmental toxins (liver)

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52
Q

What are the two sites of protein synthesis in Euk cells?

A

ribosomes free in cytoplasm

ribosomes in rough ER

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53
Q

Where do proteins translated by ribosomes in the cytoplasm end up?

A

peroxisomes, mitochondria, nucleus, cytoplasm

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54
Q

Where do proteins translated by ribosomes on the rough ER end up?

A
  1. secreted into extracellular environment
  2. integral plasma membrane proteins
  3. membrane or interior of the ER, Golgi, or lysosomes
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55
Q

The ER, Golgi, lysosomes, and the extracellular environment are essentially _______.

A

contiguous

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56
Q

When a protein ends up in the ER lumen, does it ever touch the cytoplasm before leaving the cell?

A

no, it is transported on vessicles through the golgi and is let outside the cell by exocytosis

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57
Q

What determines whether a protein will be translated on the rough ER?

A

the sequence of the protein itself, signal sequence at the N-terminus

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58
Q

What recognizes the signal sequence in proteins?

A

signal recognition particle (SRP), which binds to the ribosome

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59
Q

The mRNA for a secreted protein encodes a longer protein than is actually observed in the cell exterior. why?

A

the signal sequence of the protein was removed in the rough ER

the only way a protein can be smaller from its mRNA would be if some post translational modification happened

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60
Q

What are transmembrane domains?

A

sections of integral membrane proteins of hydrophobic amino acid residues that pass through lipid bilayer membranes

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61
Q

T/F

Transmembrane domains are translated and transported the same way as secreted protein.

A

true

from ER to golgi to plasma membrane but they are used in the membrane, not secreted

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62
Q

For a protein in the plasma membrane, does the portion of the protein in the ER lumen end up facing the cytoplasm or the cell exterior?

A

cell exterior

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63
Q

Glycosylation? where does it occur?

A

addition of saccharides to proteins

usually occurs in the golgi, but some occurs in the rough ER

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64
Q

What is the default target for proteins that go through secretory paths?

A

plasma membrane

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65
Q

What is needed if a protein going through the secretory path needs to end up somewhere other than the plasma membrane?

A

targeting signal

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66
Q

What is needed if a protein that is made in the cytoplasm needs to be sent to an organelle that is not part of the secretory path?

A

localization signal

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67
Q

for more info check out page 146

A

MCAT bio book

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68
Q

Disulfide bridges are found in extracellular proteins because the cytoplasm is a reducing environment that changes cysteine to two cysteines, would it make sense that disulfide bridges are formed in the ER lumen?

A

yes because the ER lumen is contiguous with the extracellular environment

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69
Q

Three functions of the Golgi Apparatus?

A
  1. modification of proteins made in the Rough ER, especially the modification of oligosaccharide chains
  2. sorting and sending proteins to their correct destinations
  3. synthesizes certain macromolecules (polysaccharides) to be secreted
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70
Q

The vesicle traffic to and from the Golgi is mostly ________. (direction?)

A

unidirectional

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71
Q

Retrograde traffic?

A

proteins that are supposed to be in the ER escape and must be returned to ER from the Golgi (example of traffic not being unidirectional in Golgi)

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72
Q

Part of the Golgi nearest the rough ER is the ____ stack, the part farthest from the rough ER is the ___ stack.

A

cis
Medial is in the middle
trans

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73
Q

If vesicle fusion with the Cis Golgi was inhibited, could plasma membrane proteins reach the surface?

A

no, it must follow a track (ER to Cis to Medial to Trans to cell surface)

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74
Q

Constitutive secretory pathway in golgi?

A

proteins sent in vesicles from the golgi immediately to the cell surface continuously and unregulated

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75
Q

Regulated secretory pathway in golgi?

A

specialized secretory cells store proteins in vesicles and release them only at certain times usually in response to a change (ex. pancreatic cells, B cells)

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76
Q

Where are lysosome proteins made, modified, and released?

A

made- rough ER

modified- Golgi

released- trans Golgi

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77
Q

Autophagy?

A

organelles such as mitochondria that have been damaged or are no longer functional are degraded in lysosomes (self eating)

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78
Q

Phagocytosis?

A

large matter merge with lysosomes which degrade it (ex. macrophages engulf bacteria or viruses)

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79
Q

Crinophagy?

A

lysosomal digestion of unneeded (excess) secretory products

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80
Q

What is the enzyme responsible for degradation in lysosomes?

A

acid hydrolases

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81
Q

What is the pH of the cytoplasm and lysosomes?

A

cyto- 7.4

lyso- 5

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82
Q

Can the cell be destroyed in one lysosome ruptures?

A

no because the acid can be diluted by the cytoplasm, but if many rupture the cell can be destroyed

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83
Q

What is the byproduct of enzymes in the peroxisomes? what is it used for?

A

H2O2

  • essential for lipid breakdown
  • in liver, essential for detox of drugs and chemicals
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84
Q

Even though H2O2 is a dangerous chemical, how do peroxisomes make it not harm the body?

A

contain an enzyme called catalase which converts it to H2O + O2 which protects against peroxides or free radicals

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85
Q

What are the three most common lipids in Euk membranes?

A

phospholipids (most)
glycolipids
cholesterol

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86
Q

What is a distinct feature about phospholipids and glycolipids?

A

they are hydrophobic and hydrophilic

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87
Q

What happens when phospholipids are mixed with water?

A

they arrange themselves so the hydrophobic tails are facing the interior away from the water and hydrophilic regions are facing outward to interact with water (lipid membranes)

88
Q

What happens when fatty acids are mixed with water?

A

micelles form (circle)

89
Q

Does the formation of lipid bilayer when phospholipids are mixed with water have a positive or negative delta G?

A

negative because it forms spontaneously, as the lowest energy state, without external energy input

90
Q

Why cant hydophilic molecules such as ions, carbs, and amino acids barred from passage into the cell?

A

the inside is hydrophobic, water is excluded, so these molecules are not soluble in this environment

91
Q

What molecules can pass the lipid bilayer easily?

A

nonpolar molecules such as CO2, O2, and steroid hormones, water passes through specialized channels

92
Q

Another component of the lipid bilayer is ______.

A

proteins

93
Q

What do proteins do in the lipid bilayer?

A
  • mediate interactions between cells
  • cell surface receptors bind extracellular signaling molecules such as hormones and relay signals into the cell
  • channel proteins selectively allow ions or molecules to cross the membrane
94
Q

Integral vs peripheral proteins?

A

I- embedded in the membrane, held by hydrophobic interactions

P- not embedded but are stuck to integral proteins, held by H-bonds and and electrostatic interactions

95
Q

Transmembrane proteins?

A

cross the whole lipid bilayer

96
Q

At which point in the secretory pathway would the insertion of transmembrane domains into the membrane occur?

A

in the rough ER as the protein is translated and threaded across the ER membrane

97
Q

Fluid mosaic model?

A

current understanding of membrane dynamics, membrane is seen as a mosaic of lipids and proteins which are free to move back and forth fluidly, two dimensions

98
Q

Why does the cell membrane have polarity?

A

lipids and proteins are not free to flip flop

hydrophilic proteins cannot enter the hydrophobic interior

99
Q

What is the exception to the fluid mosaic model?

A

some proteins are anchored to the cytoskeleton and cannot move

100
Q

What is a major determinant of membrane fluidity?

A

hydrophobic van der waals interactions between the fatty acid side chains

101
Q

What is the difference between saturated and unsaturated fatty acids in the membrane?

A

sat- lack double bonds, have a very straight structure and pack tightly in the membrane, strong van der waals

unsat- one or more double bonds, kinked structure and pack in the membrane interior more loosely

102
Q

How does cholesterol play a role in membrane fluidity?

A

maintains optimal membrane fluidity by fitting into the membrane interior

103
Q

If the % of unsaturated fatty acids in a membrane is increased, will membrane fluidity increase or decrease at body temp?

A

increase because of kinked structure and weaker van der waals

104
Q

Which proteins transport materials through membranes that cannot diffuse on their own?

A

integral membrane proteins

105
Q

Diffusion?

A

solute moves from high to low concentration

106
Q

Osmosis?

A

solvent diffuses instead of solute

107
Q

What will happen to the cell if it is placed in a hypotonic solution?

A

swell and burst

108
Q

What will happen to the cell if it is placed in a hypertonic solution?

A

shrink

109
Q

Isotonic?

A

solute concentration is the same inside and outside the cell

110
Q

Osmotic pressure?

A

force required to resist the movement of water by osmosis

if a solution is highly concentrated, it has a strong tendency to draw water into itself, so the pressure required to resist it would be high

111
Q

The greater the difference in tonicity across a semipermeable membrane, _______.

A

the greater the osmotic pressure

112
Q

What is transport that is any thermodynamically favorable movement of solute across a membrane (down a gradient)?

A

passive transport (no energy required)

113
Q

What are the two types of passive transport?

A

simple diffusion

facilitated diffusion

114
Q

Why are steroid hormones free to move back and forth across the membrane?

A

simple diffusion as pushed by their concentration gradients because of their hydrophobicity

115
Q

Facilitated diffusion?

A

movement of a solute across a membrane, down a gradient (integral proteins), when the membrane is impermeable to that solute (ex. glucose crossing the membrane into red blood cells)

116
Q

What are the two types of proteins (selective) used in facilitated diffusion?

A

channel proteins

carrier proteins

117
Q

What do channel proteins allow passage of?

A

each channel can only let in one type of ion down the concentration gradient, they are gated, form a tunnel for ions to pass

118
Q

Voltage gated ion channel?

A

channel that opens in response to a change in the electrical potential across the membrane

119
Q

Ligand gated channel?

A

opens in response to binding of a specific molecule like a neurotransmitter

120
Q

Can ion channels move ions against an electrochemical gradient?

A

no, only down due to facilitated diffusion

121
Q

How do carrier proteins move molecules across the membrane?

A

bind the molecules to be transported at one side of the membrane and undergo conformational change to move the molecule to the other side

122
Q

Uniports? symports? antiports?

A

uni- transport only one molecule at a time

symp- carry two substances in the same direction

anti- carry two substances in opposite directions

123
Q

Pores in the membrane?

A

tube through membrane so large that it is not selective and all molecules below a certain size may pass unless they are just small enough and have the wrong charge on its surface

124
Q

What forms pores?

A

polypeptides called porins

125
Q

What membranes have pores?

A

nuclear membrane, outer mitochondrial membrane, gram negative bacteria outer membrane

Euk plasma membrane does not have pores

126
Q

Are porins and ion channels found in the same membrane?

A

no because there would be no use for ion channels if porins were present because they are big enough to let ions in

127
Q

Saturation kinetics?

A

facilitated diffusion depends on a finite number of integral proteins so increasing the driving force increases the rate of diffusion (flux) but only to a certain point, then all transport proteins become saturated and no further increase is possible (this doesnt happen in simple diffusion)

128
Q

Active transport?

A

movement of molecules through plasma memrbane against a gradient, requires energy, involves a protein (delta G is negative)

129
Q

What type of energy input is needed for primary active transport?

A

transport is coupled with ATP hydrolysis

130
Q

What type of energy input is needed for secondary active transport?

A

transport is not coupled with ATP hydrolysis

ATP is first used to create a gradient, then the potential energy in that gradient is used to drive the actual transport of other molecules across the membrane, ATP is used indirectly, commonly coupled with the flow of sodium ions

131
Q

If a protein moves sodium ions across the plasma membrane down an electrochemical gradient, what form of transport is this?

A

facilitated diffusion

132
Q

The Na+/K+ ATPase is a ______ protein.

A

transmembrane

133
Q

The activity provided by the Na+/K+ ATPase is to pump ___ Na+ out of the cell and ____ K+ into the cell, and to hydrolyze ____ ATP to drive the pumping of these ions against their gradients.

A

3
2
1

134
Q

The pumping of Na and K by the Na+/K+ ATPase is an example of what form of transport?

A

primary active

135
Q

How do some of the K+ ions pumped into the cell make it back out?

A

leak out down its gradient by potassium leak channels

136
Q

What is the purpose of potassium leak channels?

A

maintain osmotic balance with its surroundings

137
Q

As K+ leaves the cell, what happens to the electrical charge on the inside of the cell?

A

positive charged K+ ions leave, the interior is left with a net negative charge

138
Q

Resting membrane potential?

A

-70 mV

the potential created by the Na+/K+ ATPase

139
Q

What are the three ways the Na+/K+ ATPase pump is important?

A
  1. maintain osmotic balance between cell interior and exterior
  2. establish the resting membrane potential
  3. provide the sodium concentration gradient used to drive secondary active transport
140
Q

If an inhibitor of the Na+/K+ ATPase is added to cells, what might occur?

A

the interior of the cell will become less negatively charged because the job of the pump is to pump out one net positive ion

141
Q

Why is chloride so concentrated outside the cell?

A

the cell interior has millions of negative charges so the chloride serves to balance the inside and outside of the cell

142
Q

Which are high outside the cell? which are high inside?

Na+, K+, Cl-, Ca2+

A

inside- K+

outside- Na+, Cl-, Ca2+

143
Q

Exocytosis? Products released?

A

process to transport material outside the cell in which a vesicle in the cytoplasm fuses with the plasma membrane, and the contents are expelled to the extracellular space

products released are secreted by the cell, such as hormones and digestive enzymes

144
Q

What are the three type of endocytosis?

A
  1. phagocytosis
  2. pinocytosis
  3. receptor mediated
145
Q

Pinocytosis (cell drinking)?

A

uptake of small molecules and extracellular fluid via invagination

146
Q

Receptor mediated endocytosis?

A

a highly specific cellular uptake mechanism where the molecule must bind to a cell surface receptor found in clathrin coated pit (ex. cells take up cholesterol out of the blood so they dont stick to the walls of arteries)

147
Q

Atherosclerosis?

A

build up of plaque on the walls of arteries

148
Q

Does clathrin recognize and bind to lipoproteins?

A

no, clathrin is fibrous protein inside the cell that associates with the receptors that do bind to it

149
Q

Compare and contrast receptor mediated endocytosis and active transport?

A

both import a particular substance

endocytosis- the substance ends up sealed in an endosome

150
Q

What acts as the key for a given receptor?

A

specific ligand

151
Q

Signal transduction?

A

the intracellular process triggered by the binding of ligand to its receptor on the cell surface, which activates a second messenger

152
Q

What are the three main types of cell surface receptors?

A
  1. ligand gated ion channels
  2. catalytic receptors
  3. G protein linked receptors
153
Q

What is an example of ligand gated ion channel? describe process.

A

sodium channel on the surface of a muscle cell at the neuromuscular junction

when acetylcholine binds to this receptor, the receptor undergoes a conformational change and becomes an open Na+ channel, this causes a massive influx of sodium down its gradient, depolarizes the cell and muscle contracts

154
Q

What is the role of catalytic receptors?

A

its like a protein kinase, to covalently attach phosphate groups to proteins which regulates protein activity (ex. insulin receptor-tyrosine kinase)

155
Q

Does a G protein linked receptor directly transduce its signal?

A

no it needs the aid of a second messenger

156
Q

What is a second messenger?

A

chemical signal that relays instructions from the cell surface to enzymes in the cytoplasm

157
Q

What is the most important second messenger?

A

cyclic AMP (cAMP)

158
Q

What does cAMP do?

A

it is the second messenger of epinephrine and glucagon which causes energy mobilization (glycogen and fat breakdown)

159
Q

What are the 6 steps in G protein mediated signal transduction stimulated by epinephrine?

A
  1. Epinephrine arrives at the cell surface and binds to specific G protein linked receptor
  2. cytoplasmic portion of the receptor activates G proteins, causing GDP to dissociate and GTP to bind in its place
  3. the activated G proteins diffuse through the membrane and activate adenylyl cyclase
  4. Adenylyl cyclase makes cAMP from ATP
  5. cAMP activates cAMP dependent protein kinases (cAMP-dPK) in cytoplasm
  6. cAMP-dPK phosphorylates certain enzymes, mobilizing energy (enzymes necessary for glycogen breakdown activated)

G here is a stimulatory protein

160
Q

What do inhibitory G proteins do?

A

inactivate adenylyl cyclase

161
Q

What happens when G protein activate phospholipase C?

A

increases cytoplasmic Ca2+ levels

162
Q

What provides the animal cell with structural support?

A

cytoskeleton- also allows movement and transport

163
Q

What types of proteins is the internal cytoskeleton composed of?

A

microtubules- thickest
intermediate filaments
microfilaments- thinnest

they have quaternary structure

164
Q

The microtubule is a hollow rod composed of what two globular proteins?

A

alpha tubulin
beta tubulin
(polymerized noncovalently)

they form a alphabeta tubulin dimer, many dimers can stick to form a sheet which rolls into a tube

they can get longer or shorter by adding or removing tubulin monomers

165
Q

Microtubule Organizing Center (MTOC)?

A

side that cannot elongate because it is anchored

166
Q

Centrioles?

A

structure composed of a ring of nine microtubule triplets, found in pairs at the MTOC of a cell, they duplicate during cell division and serve as the organizing center for the mitotic spindle

167
Q

Aster?

A

microtubules that radiate out from the centrioles during mitosis, star shaped

168
Q

Polar fibers?

A

microtubules connecting the chromosomes to the aster

169
Q

Mitotic Spindle?

A

the whole assembly of centrioles, aster, and polar fibers

170
Q

Two pieces of evidence that centrioles arent essential in mitosis?

A
  1. plants lack centrioles but still undergo mitosis

2. experimenters have removed centrioles from animal cells and mitosis still proceeded

171
Q

Cilia in Euk?

A

small hairs on the surface which move fluids past the cell surface (ex. mucociliary elevator- respiratory tract cilia sweep mucus)

172
Q

The only human cell which has a flagellum is the _____.

A

sperm

173
Q

What is the structure of cilia and flagella?

A

9 + 2 arrangement of microtubules

174
Q

Dynein?

A

microtubules are bound to their neighbors by this protein which causes movement of filaments past one another

175
Q

Basal body?

A

cilium and flagellum are anchored to plasma membrane by this protein and it has the same structure of a centriole

176
Q

How are microfilaments formed?

A

in the cytoplasm form polymerization of the globular protein actin

177
Q

What are microfilaments responsible for?

A

for gross movements of the entire cell, such as pinching parent cell into two daughter cells and amoeboid movement

178
Q

Amoeboid movement?

A

changes in the cytoplasmic structure cause cytoplasm and the rest of the cell to flow in one direction

179
Q

What makes intermediate filaments different from micro tubules and microfilaments?

A

heterogeneous, composed of a wide range of polypeptides, more permanent, resists mechanical stress

180
Q

Epithelium?

A

layer of cells that form a tight seal, preventing items from freely moving between lumen and body

181
Q

Tight junctions?

A

occluding, seal the prevents movement of substances across the cell layer, found between epithelial cells lining the intestine and the blood brain barrier

182
Q

Desmosomes?

A

epithelial cells held tightly together but do not form a complete seal (ex. skin)

183
Q

Gap junctions?

A

connected by holes that allow ions, amino acids, and carbs but not polypeptides or organelles to flow back and forth between them, allow cytoplasms to mix(ex. heart muscle cells- allow action potentials to pass from one to the other)

184
Q

Apical surface?

A

surface of the plasma membrane facing the intestinal lumen

185
Q

Basolateral surface?

A

other side of the cell facing the tissues

186
Q

Will a transmembrane protein inserted into the apical surface of an intestinal epithelial cell diffuse in the plane of the plasma membrane to reach the basolateral surface?

A

no because tight junctions prevent it from diffusing to the other side

187
Q

How are desmosomes anchored to the plasma membrane?

A

by a plaque formed by the protein keratin, intermediate filaments attach

188
Q

What happens in the S (synthesis) phase?

A

cell actively replicates its genome

189
Q

What is the M phase?

A

includes mitosis and cytokinesis

mitosis- divide cellular components in half
cyto- physical dividing

190
Q

What is between the M and S phases?

A

G1 and G2 phases

191
Q

What are the gap phases plus the S phase known as?

A

Interphase

192
Q

The cell spends most of its time in what phase?

A

interphase

193
Q

What is a cell that is permanently stuck in interphase?

A

Go

194
Q

The more specialized a cell is, the ____ likely it is to be able to reproduce.

A

less

must be replenished by stem cells

195
Q

Oncogenes?

A

mutated genes that induce cancer

196
Q

What would happen if Mitosis began during the S phase before the entire genome is replicated?

A

the genome would be fragmented and incomplete in each daughter cell

197
Q

What are the 4 phases of Mitosis?

A

Prophase
Metaphase
Anaphase
Telophase

198
Q

What is the first sign of prophase?

A

the genome becomes visible after not being visible in interphase

199
Q

At the beginning of prophase, what can be seen?

A

46 chromosomes

23 pairs

200
Q

Two copies of the chromosome separated by a centromere is a ____ ______.

A

sister chromatid

201
Q

What are homologous chromosomes?

A

equivalent but nonidentical and do not come anywhere near each other during mitosis

202
Q

What are other important events that take place during prophase?

A

nucleolus disappears
spindle and kinetochore appear
centrioles move to opposite ends of the cell (cell has two MTOCs called asters)

203
Q

What is the last step in prophase?

A

prometaphase- nuclear envelope converts itself into many tiny vesicles

204
Q

What happens in metaphase?

A

all chromosomes line up at the center forming the metaphase plate, this happens because the kinetochore of each sister chromatid is attached to spindle fibers that attach to the MTOC

205
Q

What happens during Anaphase?

A

spindle fibers shorten and the centromeres of each sister chromatid pair are pulled apart, the cell elongates and cytokinesis begins with the formation of a cleavage furrow accomplished by a ring of microfilaments encircling the cell and contracting

206
Q

What happens in telophase?

A

nuclear membrane forms around the bunch of chromosomes at each end of the cell, chromosomes decondense and a nucleolus becomes visible within each new cell, each daughter nucleus has 2n chromosomes

207
Q

What is karyotype?

A

display of an organism’s genome

208
Q 
Euk chromosomes generally only have one of which of the following?
A. reading frame
B. origins of replication
C. promoter
D. centromere
A

D

if it had more than one centromere, it could be pulled apart at different ends and be torn

209
Q

Retrograde? Anterograde?

A

Retro- moving backwards

Antero- moving forwards

210
Q

Where are steroid hormones stored in the cell?

A

they are not stored because they can diffuse through the lipid bilayers at any time

211
Q

What is the order of signals leading to the formation of cAMP?

A

Epinephrine -> GPCR -> G proteins -> adenylyl cyclase -> cAMP

212
Q

The nuclear membrane is absent in which of the following phases of mitosis?

Anaphase
Telophase
Metaphase

A

Anaphase

Metaphase

213
Q

Both the Golgi complex and rough ER contribute to protein modification through all except:

phophorylation
creation of disulfide bridges
glycosylation
creation of peptide bonds

A

creation of peptide bonds

this occurs during translation, prior to any modification

214
Q

T/F

Phospholipase C and adenylyl cyclase are examples of enzymes found in lysosomes.

A

False

215
Q

T/F

Cytochrome C is located in the inner mitochondrial membrane and undergoes redox reactions.

A

True

MCAT TPR Biology (7 decks)

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